title: Dopaminergic modulation of motor coordinaton in Parkinson's disease.
abstract: BACKGROUND
  We applied the idea of synergies and the framework of the uncontrolled manifold hypothesis to explore the effects of dopamine replacement therapy on finger interaction and coordination in patients with early-stage Parkinson's disease (PD).
  
  
  METHODS
  Eight patients performed single-finger and multi-finger force production tasks with both the dominant and non-dominant hand before (off-drug) and after (on-drug) taking their dopaminergic medications. Synergy indices were defined as co-varied adjustments of commands to fingers that stabilized the total force produced by the hand.
  
  
  RESULTS
  PD patients showed significantly lower maximal finger forces off-drug compared to the on-drug condition, while indices of finger individuation (enslaving) were unchanged. The synergy indices were weaker during steady-state force production off-drug compared to on-drug. Anticipatory adjustments of synergies prior to the quick force pulse initiation were delayed and reduced off-drug as compared to the on-drug condition. These drug effects were observed in both the symptomatic and asymptomatic hands of the patients whose symptoms were limited to one side of the body.
  
  
  CONCLUSIONS
  The study demonstrates dopaminergic modulation of motor coordination in PD and supports that the analysis of different components of multi-finger synergies offers a set of indices sensitive to the effects of dopamine replacement therapy in early-stage PD. The results suggest an important role of the basal ganglia in synergy formation and in feed-forward synergy adjustments. Future studies using these methods may yield more objective, quantitative biomarker(s) of motor coordination impairments in PD, and better understanding of subcortical involvement in the neural control of natural actions.
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, Rec. Hall-268N, University Park, PA 16802, USA.
authors.forename: Jaebum
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Pharmacology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
authors.forename: Mechelle M
authors.initials: MM
authors.lastname: Lewis
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, Rec. Hall-268N, University Park, PA 16802, USA; Department of Neurology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Pharmacology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Radiology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA; Department of Neurosurgery, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Huang
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, Rec. Hall-268N, University Park, PA 16802, USA. Electronic address: mll11@psu.edu.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Latash
mesh_terms: D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D005260:Female; D005385:Fingers; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D010300:Parkinson Disease / Q000188:drug therapy* / Q000503:physiopathology; D011597:Psychomotor Performance / Q000187:drug effects*
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa
keywords: Feed-forward control; Finger; Parkinson's disease; Synergy; Uncontrolled manifold hypothesis